Improvement of the Operational Characteristics of the Condenser K-33160 in Kozloduy NPP

Topic :

Flow Accelerated Corrosion

ABSTRACT :

Modernization Program is being performed on Units 5 and 6 of Kozloduy NPP related to the Plan lifetime management for safety upgrading through replacement of the equipment with expiring design life and of critical equipment and the improvement of work efficiency and operating conditions. Replacement of the copper containing alloys of the equipment of secondary circuit was made. The upgrade of the turbine condenser K-33160 was carried out to improve its operational characteristics. Among the numerous factors having impact on the flow accelerated corrosion and consequently on the operation of the equipment is water chemical regime of the secondary circuit. The choice of water chemistry depends mainly on the construction materials:

• temperature and velocity of flows;
• reagents type selection and distribution;
• contamination of the secondary coolant.

Thermal calculation by zones let us define the configuration of the tube bundles in the condenser which would provide sufficient thermal loading to all condenser tubes. That would increase the condenser heat efficiency. According to the new configuration of the tube bundles 24 new modules containing 26832 stainless steal tubes each were replaced in the condenser. The condenser upgrade leaded to changes in the water chemical regime of the secondary circuit. That resulted in reduction of mass transfer of corrosion products in the secondary circuit.